Add control over associations params

[ssnickolay]

Closes #15

• [x] Implement new nested parameters logic.
• [x] Change integration specs with using new logic.
• [x] Add new documentation page about parameters.
• [x] Сheck for correctness all docs snippets.
• [x] ~Support multiple keys.~
• [x] Pass the parent record as a param.

[ssnickolay]

let's rename ByBlockFilter and ByKeyFilter to just BlockFilter and KeyFilter respectively.

I agree :+1:

And for AllowFilter and DenyFilter, maybe, it would be better to use something like PassFilter and NullFilter.

I think NullFilter not very good class name, because it's sounds like EmptyFilter or WithoutFilter(

[palkan]

I think NullFilter not very good class name, because it's sounds like EmptyFilter or WithoutFilter(

What about using Proxy instead of Filter? Then NullProxy makes sense

[ssnickolay]

What about using Proxy instead of Filter? Then NullProxy makes sense

Hm, I like it :+1:

[ssnickolay]

@palkan It looks like we're done. Can you look again, please?

[ssnickolay]

@palkan done :+1: Feel free to merge to master)